Glossary of Internet Terms

©2007 by Walt Howe

Select the first character of the term you want to look up or use the Search link below.

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Letter T

A digital communications circuit that transmits at 1.54 Mbps.

A digital communications circuit that transmits at 45 Mbps.

In reference to web pages, a tag is an HTML command used in laying out a web page and providing links to resources.

Acronym for “There Ain’t No Such Thing As A Free Lunch”. From Robert Heinlein’s The Moon Is a Harsh Mistress.

Transmission Control Protocol/Internet Protocol. The protocols that are the basis for transmitting and routing data packets on the Internet. The Internet Protocol is the one thing that all current Internet sites have in common. The basic TCP/IP model has five layers of interaction:

  • Physical or Data Transport Layer. This most basic layer moves data over cables based on the physical address of each Network Interface Card (NIC). The most common types are ethernet and token ring.
  • Data Link Layer. This layer frames the packets of data that are sent through the network. PPP, frame relay, and X.25 operate at this layer. Bridges connect local networks at this layer.
  • Network or Internet Protocol Layer. This layer puts an Internet Protocol wrapper around the data with source and destination addresses in its header. Routers, which connect networks together, operate at this layer.
  • Transport Layer. This layer governs the setting of suitable packet sizes, segmenting and reassembling data, detection of errors, and flow control.
  • Application Layer. This layer provides for standard interfaces for such functions as message handling and file transfer and remote login. It allows, for example, for different e-mail programs to be used, as long as they conform to the standard interface. This layer in TCP/IP corresponds to the session, presentation, and application layers in the OSI model.

See History.

Telnet is a protocol that lets you log in to a remote computer and use programs and data that the remote owner has made available, just as if it were your local computer. For more information and examples, see the Telnet FAQ.


Acronym: The End Of The Word As We Know It. Perhaps invented by those pessimistic about the Year 2000. See millenium bug.

A series of messages with the same subject. It consists of an original message and all the replies and replies to replies that follow. Sometimes the replies will stray from the original subject, and this is called ‘thread drift’.

Three Letter Acronym

Top Level Domain. See domain name.

TN3270 is a special type of telnet that is sometimes needed to connect to IBM mainframe sites. Regular telnet will often work, but if you have trouble with keypresses and commands, you may need a tn3270 client to add to your software.

Acronym for “The Other Service.” Often used among a group of people who have switched from one on-line service to another. The service they came from is “the other service.” It often refers to Genie or AOL, but can refer to Compuserve or Prodigy or even the late NVN, depending on where a group originated.

Terms of Service.

Acronym for “The Powers That Be”; refers to the management of the activity being discussed.

An Internet utility that will show you the full connection path between your site and another Internet address. You can run your own traceroute software with a PPP or net connection. Windows 95, NT and beyond include a traceroute program (tracert.exe) which you can use from Start/Run. First type command (or cmd in XP) to call a DOS window. Then type the command tracert (or any other address).
transit spam
A form of e-mail spam which is sent through another Internet mail server than the one it originates from, usually with forged headers to make it look as if it originated from the through site, rather than the actual originating site.
transparent GIF
A type of GIF image where one color, usually the background of the image, has been selected to appear as transparent. When placed on a web page, any background color or tiled image will show through the transparency. It is the way to put graphics with shapes other than the usual rectangles on a page. See GIF.

Trojan horse
A destructive program that masquerades as a harmless one. When you run a Trojan horse program, believing that it has a useful function, it will instead, for example, erase your hard drive. See virus and worm.


  1. An outrageous message posted to a newsgroup or mailing list or message board to bait people to answer. Trolling is a form of harassment that can take over a discussion. Well-meaning defenders can create chaos by responding to trolls. The best response is to ignore it.
  2. Also, the person who posts such messages.
Chat shorthand for “ta ta for now”. See bfn.
twisted pair
A twisted pair is a pair of insulated wires that twist around each other repeatedly in a spiral pattern along the length of the wires. Twisting them rather than running them side by side reduces electromagnetic interference. Ordinary telephone cable in the house usually consists of two or three twisted pairs, with each wire coded in a different color insulation. Twisted pairs surrounded by a shielding ground layer are known as shielded twisted pair. Twisted pair is often used in ethernet LANs.

(last updated 22 October 2012)